How To Deal With Non-recognition Aggression In Cats

Ever come home to find your once-friendly kitties suddenly at odds with each other? Welcome to the perplexing world of non-recognition aggression in cats. This unexpected scenario can leave you startled and concerned about the harmony in your furry family. But why does it occur and, more importantly, how do you handle it?

In this article, we get into the psychology of our four-legged friends, exploring why such a drastic change in behavior can happen seemingly overnight. From unexpected trips outside the house to the effects of a visit to the vet, we'll examine the triggers that can turn your peaceful household into a furry battlefield.

We'll also share insights into preventative measures and steps to restore harmony among your pets. Consider this your guide to understanding and handling non-recognition aggression, a scenario that could become a reality for any multi-cat household.

But remember, this isn't just a problem - it's an opportunity to better understand your pets and their unique behaviors. Read on, and let's navigate this together.

Aggressive domestic cat sitting on a window sill, How To Deal With Non-recognition Aggression In Cats

Unexpected Rivalry

Picture this: your cats, typically the best of buddies, are now sworn enemies. The change? A brief stint of one cat outside your home. It sounds strange, but it's a common problem in the world of cats, known as "non-recognition aggression."

The Surprising Trigger: A Trip Outside

That's right. Just one of your cats spending some time outdoors can trigger this unexpected shift. When they come back home, the other cat perceives them as a stranger, a potential threat to their territory. The cause of this confusion? A change in scent that your indoor cat doesn't recognize.

Understanding Non-recognition Aggression

This puzzling behavior goes by the name of "non-recognition aggression." While the term may sound complex, it simply describes the reaction of a cat to a housemate they don't recognize anymore. This phenomenon can leave you scratching your head, wondering what happened to your harmonious household.

Why Should You Care?

If your home houses more than one cat, pay close attention. Non-recognition aggression could strike at any time. The key to restoring peace? Understanding this issue and knowing how to handle it effectively.

Why does non-recognition aggression even happen?

I have two cats, Shadow (10 years old) and Sylvester (5 years old). Shadow has a gum disease and I took her to the vet last Friday. I brought her back in the house and put her down on the ground and Sylvester attacked her, ripped off her bandage, her collar and had tuffs of her fur under his claws.

From the cat behavior forum

Why are we seeing this type of behavior in cats? What would cause a healthy cat to turn on the sick cat and attack? After all, they used to be good friends before.

The answer is that they probably don't even recognize the cat at that very moment.

This sounds strange to us as we rely on sight to recognize other people. For cats, however, the more relevant sense is the scent.

The cat returning from the vet doesn't smell like the cat they knew before. This cat is covered with strange scents to the point that they become unrecognizable.

The resident cat therefore reaches a conclusion: Someone swapped his former friend with a stinky alien.

Cat behavior experts call this "Non-recognition syndrome." Some believe it's not only the strange smells that were picked up by the cat while outside the home. The new smell may also be the result of the cat's own fear.

Having spent the day in unfamiliar surroundings, the returning cat could very well be very stressed and fearful. They may still be in pain or under the influence of anesthesia drugs, and this is something other cats could pick up on, whether through smell or body language. Those cues - invisible to us - could also trigger an aggressive response.

For some cats, the smells from a veterinary clinic may be too frightening in their own right. Even if they recognize the returning cat, they may still lash out in response to the smells that remind them of their own scary experience at the clinic.

Is non-recognition aggression triggered only by vet visits?

Non-recognition aggression can be seen in any situation where the cats were separated. A vet visit is the most usual scenario because that's a common occasion where one cat leaves home and returns hours or days later.

The same type of behavior can also happen following a visit to the groomer, but most cats don't require such visits, making this a rare trigger.

When an indoor-only cat manages to get outside for a few hours or even days, he or she may experience the wrath of non-recognition aggression upon returning home.

The longer the time spent outside, the more likely he is to pick up new and unfamiliar scents that can trigger the response in other household cats.

How to deal with non-recognition aggression in cats?

Whenever one of your cats is separated from the others, you should keep this type of aggressive behavior in mind.

There are things you can do to try and prevent an onset of non-recognition aggression, but if all else fails, you need to be prepared to deal with the situation.

Deal with stress early on

Stress makes cats more prone to aggression in general. Just like in humans, elevated levels of stress can put a cat "on edge."

When a stressed-out cat is confronted with the unfamiliar scents on the returning cat, he or she is more likely to lash out.

Use care when bringing a cat back home from the vet

Don't just waltz into your home and put the cat on the floor.

Instead, keep the returning cat in a separate room for a few hours to make sure they are feeling better and more relaxed. If Kitty underwent anesthesia, make sure the effects have passed, and they are ready to face the world again.

Keeping the cat in a separate room gives them time to groom and regain some of the familiar scents of your home.

Before allowing the cats to meet, grab a blanket or a cloth that your cats regularly come in contact with and rub it on the returning cat. Your aim is to re-apply familiar scents to cover up the "vet stink."

Have the cats meet each other in a gradual way. Open the door to the separate room to an extent that allows mutual sniffing but allows you to cut the encounter short by shutting the door if needed.

Remain calm while the cats meet each other and avoid staring directly at either cat. At the same time, do keep an eye on them and be prepared to step in.

What to do if one of the cats becomes aggressive

A certain amount of hostility is normal in this situation. If one of the cats hisses and then moves on, that's ok.

However, if either cat lashes out, you'll have to break up the catfight by placing some kind of barrier between the cats.

Be careful! If one of the cats is very upset, they can quickly re-direct that aggression towards you. Always keep your hands away from a scared or aggressive cat.

Keep calm and avoid shouting or reprimanding any of the cats, regardless of their reactions. They're not misbehaving. They're just being cats, acting on sensory input you don't have access to.

If the cats are very hostile towards each other, you may need to separate them for a few days until both sides calm down and then introduce them again as if they've never met before.

Use our guide: How to successfully introduce cats and follow through. Don't rush the process to give the cats the best chance at becoming friends once again.

Have you ever experienced non-recognition aggression with any of your cats?

Share your story in a comment below and let us know what happened.

As always, if you need more help, share your experience in our cat behavior forum where members can support you in your efforts to deal with non-recognition aggression.

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36 comments on “How To Deal With Non-recognition Aggression In Cats”

Bob n Trix August 3, 2022

The tuna worked for us too. Thank you for posting this.

SNC22 May 7, 2021

This is happening to us now. We have three cats. A gray (male), a black (male) and a tuxedo (female). They are all fixed. We left some rugs outside accidentally for a couple days and we brought them back in without thinking. We think a random cat sprayed it and left his scent and when we brought them back in, our tuxedo went crazy. She attacked our other two cats multiple times. She has never done this before. We took her to the vet and medically she's fine and healthy. We have been working to get the strays out of our yard and slowly re-introducing the boys to her. Unfortunately, the scent is in our yard, and every time we go out, we are bringing it in...and when she catches the scent, it triggers her. We're really having a hard time with it, but the vet ensured we just need to get rid of the strays and re-introduce our tuxedo, and over time she should be fine. Our three cats have been together for 3 years with zero problems. They love each other. Now because of this scent everything is thrown off balance..

ANDREA ANDERSON March 16, 2021

Im devastated my boys have been together since birth and were rescured at18 mths and are house cats. ive had to seperate them.after an overnight vet stay. I live by myself. The poorly cat is jumping at the door to get out however the brother is not excepting him i have spent the night between two rooms to try and settle them due to the crying and escape attempts. This is do stressful.

James November 18, 2020

We are going through this now. We have two cats a boy Kenji and a girl Kush, who have been together every day since birth. They've been to different places together, but they are never usually apart. They tend to do everything together, cuddling, cleaning each other etc. We brought Kenji back from getting castrated yesterday, and feel ignorant to say we just set him down in the main room and let him out. I wish we would have known this could happen. Kush instantly went and hid and then starting acting very aggressive, growling and hissing. We've kept them separate since then, but its difficult because he is desperate to try and see her. Neither of them are used to being alone either, so my girlfriend and I ended up sleeping in different rooms with a cat each (they are both very vocal cats). Our apartment isn't very big so its quite difficult to keep them out of each others way. Hes now in a room with one of us most of the day, which has a glass door and she generally has a bit more of the house. She definitely seems less stressed then before, but she still hisses if they are both near the glass door. We then put her in a different room. We've rubbed him with a towel which smells like her, and done our best to make him smell usual, but she's still not happy to be near him. We've been told that playing with them near each other may be a good thing to try, but other than that we are running out of ideas. Any advice would be much appreciated!

Furballsmom November 27, 2020

Hi! Please consider registering with The Cat Site, (it is free) and posting in the forum that's dedicated for this sort of thing, where members will see your post and provide suggestions and advice. The forum is https://thecatsite.com/forums/cat-behavior.5/ and if you're unfamiliar with forums, this may help; https://thecatsite.com/c/how-to-create-a-new-thread/

Annie November 30, 2020

I'm living the same story here, 2 sisters that grew up together. 1 went to the vet for 24h and the other stayed home. Had no clue that that existed, was possible, and now it's just no fun. Are yours friendly again ? It's been almost 48h for mine and the one that stayed home is still hissing at the other one.

JP December 13, 2020

I had this happen last night. My girl kitty had a 2 hour vet visit and came home to a hissy brother. She wasn’t feeling well and this was the last thing she needed. He is also a very nervous kitty. They’re a 3 year old bonded pair. I usually take them both to the vet instead of just taking one, you know for moral support! Anyways, this was an emergency visit so I only took my girl kitty. I stayed up late trying to keep an eye on them and eventually had to completely separate them. I even tried catnip! These two are really different than any other cats I’ve had the pleasure of taking care of. I’ve never had cats that do not like being alone at times but these two stick to me like glue as well as each other. Needless to say, this whole event was stressful for all involved. Even this morning the boy was still hissy towards his sister. So, after a quick internet search, my husband found out a really cool trick. Rub both kitties with the juice from canned/pouch tuna. That’s it!!! The tuna smell overwhelms the unrecognized kitty smell and by the time they get it all licked off they’re friends again!!! I literally rubbed them both down with tuna juice and my boy immediately sniffed and started licking his sister! Problem solved in less than a minute. I hope this helps everyone!!! Side note: tuna worked because they both love it. I didn’t have to saturate the kitties, I just put enough to overwhelm the other smells.

happyfeet October 24, 2021

I'm curious to hear if this resolved the problem long term for you. Sounds like it worked really well right away and I'm wondering if it lasted or if this ended up being a short term solution.

KazW June 21, 2022

Oh my days!! How do I say thank you? Our two cats went outside, came back in and were growling and hissing at each other non stop. They had never even raised a claw to each other in 3 years before this point! So I frantically googled what to do and read your comment, by this point we were willing to try anything, we lightly rubbed tuna water into their coats and instantly they started grooming themselves and went back to interacting normally!! Needless to say I'm bulk buying tuna from now on! Thanks again!

L O October 5, 2024

Hi JP. I wish i could try that trick. The problem is that my kitty, Oakland, is seriously injured and had surgery. Our house caught fire, and my neighbor was cat sitting both Oakland and his sister Berkeley. I came home and found Oakland crying. He turned out to have hug wound on hind leg. He's bandaged & stitched up, and after the hospital released him he came to the hotel with me. It was over 2 weeks ago. My neighbor told me she could no longer cat sit Berkeley so i had to bring her to the hotel. Well, even though she's been with Oakland all her life, and before she was born in the womb, she no longer recognizes him. She hisses like crazy. The only place to get away is the bathroom, and the door must be open as there's only one litter box. Here’s the thing: Oakland has big bandage over his wound that has to be changed daily by vet ($$$$$, it costs average of $425.00 each time). I started a gofundme as i cannot afford the high costs: Well, the vet put plastic cone around his neck so he won’t lick himself, because if he does, the wound will get infected, and he’ll have to be re-bandaged, more $$$ and hassle. I had to put one on Berkeley as well so she won’t lick him. So i can’t dump tuna on him, and let her lick him. I thought about putting it only on the parts of him that aren’t bandaged but probably she’ll lick his wound anyway. Berkeley is not drinking water, is hardly eating anything, and is losing her voice. I hold the water under her mouth as it’s hard to access bowls with the cone, but she won’t drink. I have called the vet and am waiting for call back. Tried the rubbing kitty with sock and giving sock to other kitty to smell. But all the tricks they recommend here take several days, and that will be really hard. I hope someone has an idea for me. thanks LO

Rose June 12, 2022

Same here. Vet visit for one. Cat at home has become very aggresive. 6 weeks now and we have tried all recommendations to no avail. Last resort us rehoming one of them.

ANDREA ANDERSON March 17, 2021

Hi James can i ask how the cats are . Im going through same thing now but living alone in between two rooms. Im so sad and Jax my poorly cat has been daily visiting vet for checkup im on day three and had to buy a cage for nighttime to prevent jax jumping at door handle to allow me to get some sleep. It feels like ive put him in cat jail 😪. Ive read loads of advice but any tips be great.

Nic October 28, 2020

I am experiencing this now. My two tabby cat sisters had occasional grumbles but nothing major. 2 weeks ago Trixie was savagely attacked by something causing major injuries to her ear and skull and significant blood loss due to a pierced carotid artery. She had to have a blood transfusion, her ear canal removed, and head surgery. She returned home after a week, shaved half of her head and all around her neck and shoulders. She looks very different and is still recovering. The vet said due to the length of time away her sister may not recognize her. Pixie didn't and was very aggressive towards her., Trixie is now deaf in one ear and her facial nerve was traumatized so she stares in one eye. I have been keeping them separate to all the poorly one to recover and have tried Feliway and short meet sessions, but the minute the healthy cat sees her sisters shaved head she growls, snarls, and hisses, I have got her a camouflage necktie collar to cover her neck and shoulders but that doesn't help the face, She responds the same whenever she sees the patches on her head. It's been 10 days and there's a small improvement but they can only be in the same room for about 15 minutes. I will try the scent soaked cloth from above and see if that helps! Any other suggestions welcome. Thanks

MarkMDP November 11, 2020

Hello! You are welcome to join the forums (it's free!). The Cat Health forum is a good place to start a thread here: https://thecatsite.com/forums/cat-health.4/ Please note that no online advice beats professional diagnosis.

Kellie October 19, 2020

I have 2 cats, Belle and Pumba, both females.. Normally Belle has a general dislike of other cats but she and Pumba have been raised together and when no one is looking Belle is affectionate and grooms Pumba... I should also preface this by advising Pumba is a mama cat, this is her 5th or 6th litter. She has never been an aggressive mama, growling just a bit when anyone gets too close to babies, usually only for the first couple weeks then she ishours. Her current litter is 3 weeks old. Recently, Belle got outside for a couple of hours...when she got back inside Pumba went absolutely NUTS on Her, and has been fiercely attacking her. To the point where I fear for Belle's safety. I have to keep them separate. I have been told it could be non recognition aggression, but the weird thing is, after a couple of fiercely attacks, they both slept on my bed for a couple of hours when all of a sudden Pumba went nuts again, and again today when I was in the shower. A friend said if I bathe them both in the same bath water (not at the same time...one after the other...) it may help because Pumba would recognize her own scent on herself.....

Ryan April 11, 2020

I have 2 cats. Mother(Isis)and son(Sinbad). She is Himalayan Persian mix 6 yrs old. He is 5 yrs old. I already knew about non reconition aggression behaviors. I have had it happen when I moved to a new home. The mother is always the agressor. It happens when I take him to the vet and just recently gave him a bath. I wont wash their blanket I let them bed on anymore. Thanks for the great advice

Michael Brown August 4, 2019

Threecozycats said:
We think this could be happening with our two cats who are littermates. They got along just fine until about 1.5 years ago when the female started growling/hissing at the male every time he walked in The room and/or attacking him just for walking by. Want to say this started after a vet visit for the male being sick but cannot remember as it was so long ago. This behavior has progressively gotten worse despite feliway diffusers and calming collars. It’s gotten to the point where they cannot be in the same room together and she pretty much has isolated herself to our bedroom. Now the male is exhibiting anxiety and anxious behaviors and the fighting has just gotten worse. Is there any way to manage this now that it has been going on for so long? Feel like we have tried everything under the sun. Also both got a clean bill of health from the vet so we have ruled out any medical issues.

This is heartbreaking. I'm not sure if there's a good answer. I really think vets have to be more cognizant of this and advise all of their customers about these dangers. It's probably best to bring them in together. Here's my guess--based on our experience. Initially, the hissing occurred after a vet visit. This would have been due to the different smell--and cats recognize each other through smell. But that would have worn off after a couple of days. I think after the initial hissing or attack, the attacked cat becomes fearful and releases whatever fear hormones there are--the other cat picks up on it and reacts aggressively--then there's a cycle of behavior that gets established. The key may lie in the immediate return from the vets and separating them until the smells are back to normal. In your case, now it seems like there is a behavioral pattern that needs to be addressed. Have you tried a cat behaviorist specialist to come in and see if he/she can fix it?

Kez said:
We have 17 month old brother sister siblings who we keep probably 97% of the time locked up inside. We have a large 4 bedroom house with a two and a half car garage all well equipped with several litter boxes, scratching posts, toys and plenty of free shelving for them to climb up on. They are only ever outside if we are home (they don't wander far) and we never leave them out at night either. We are very interactive with our cats, playing with them all the time, chat away to them - they quite often chat back (cute) Maisie especially likes to stay close but everything is on her terms when it comes to picking her up for cuddles where as Stuart loves cuddles and play fighting with my Husband. He is a bit of an explorer and will go for a wander to the paddocks behind us when allowed out. Stuart is a much larger cat than his sister Maisie and has on the odd occasion thought it would be a good idea to bail her up, much to her protest. We never hear Stuart letting out the blood curdling cat scream but Maisie will. What we are confused about is that Stuart, when confronted by any of the neighbour's cats, he either runs for his life or becomes quite submissive - much like Maisie when Stuart has a go at her. BUT. Maisie, as tiny as she is, has no problem having a go at any of the neighbourhood cats should she feel threatened, even coming to Stuart's aid if need be. Why do the roles get reversed and why does Stuart just randomly do this to Maisie? Any help or advise would be much appreciated as getting rid of either of them is not an option and if we can "nip" this in the bud now, would be great. Cheers from NZ

Context. In your house they have defined roles. Cats operate on a hierarchy--there's almost always a dominant cat--in this case Stuart. That doesn't necessarily mean aggressive. Outside, their roles/behaviors might be different. Not sure why Stuart does that to Maise, he may be reading her body language and a bit of fear. Not sure how to help--but I did see a show in which an animal behaviorist came in to a house in a similar situation and retrained the submissive cat how to act so as to not be targeted.

We have two cats, a male (6 years old) and female (5 years old). They adore each other. The male recently got sick and made several trips to the vets. When he returned from his last visit, the female was very aggressive towards him and attacked. She had never done that before. It was distressing to say the least because the male was weak. We separated them. With her, I knew the aggression was due to his new smell. But, he had started to hiss back at her because of the attack and had looked distressed. We worried that the dynamic between them had changed as he, the male, was putting out fearful, defensive signals. Cats are hyper sensitive to body language. The vets had advised us to keep the cats separated for 2 weeks to a month. My instincts told me otherwise based on knowing our two cats. I wanted to re-introduce them quickly so as to not develop a rift. I'm not saying this is the way to do it for everybody, I just had a hunch it might work for us. That night, when the female was very tired and sleeping, I brought the male in. Then, I let him roam around. She saw him. Before there was a face to face, I grabbed a laser so as to distract them both. They both focused on the laser and chased it. Then, as we finished, I quickly fed them their favorite snack out of my hand. They sat side by side focusing on the food. Finally, that night, they slept in their usual chair together. There were the odd hisses but they were basically back to normal. As the days passed, more and more their normal relationship resumed. The male was still hesitant of her but as time wore on, that changed. For us the key was in avoiding the stares and head on confrontations yet letting them get familiar by being in the same environment together. I did it through distraction and by petting both of them to exchange each others' smells. They were in the same environment but were not focusing on one another. I hope this helps anyone else going through the same situation.

Cat Mom June 11, 2020

This helped so much! The at home cat was mostly hissing and his tail would get really big. we kept them separated for 24 hours but we live in a small apt and keeping them apart for a week seemed very difficult. Then I saw this comment and tried it and it helped! We’ve been plying them with food and toys for over an hour. Our one guy is still on edge but it’s a huge improvement!

Summer November 1, 2020

Tremendously helpful. Thank you so much.

kitty chew October 21, 2018

I'm having this problem also. Just brought my cat Smokey home from a traumatic 3 day stay at the vet with a virus, to have his sister and best buddie, hiss at him. She is being horrible towards him, doesn't even want to stay in the house with him. She has been hiding in the cat run.

terischlem September 29, 2018

Still dealing with this non recognition aggression, since one of our cats got a lion cut on Monday. He had alot of mats & some were starting to pelt. Andy was at the Vet’s office for 8 hours getting shaved down in short increments. Now his sibling sister is a bully toward him. She hisses & appears like she may lunge after Andy. We have tried separating them. We bought a Feliway diffuser & a Feliway spray bottle, to spritz around tables & under beds where they hang out. Andy’s sister(from the same litter), is still angry at Andy. We will give it one more week, but if Zoey doesn’t stop her hissing & bad behavior, we are thinking about giving her up. It is sooooo sad to witness this aggression. They were bosom buddies before. Not they are enemies. Andy is just Andy...& Zoey now sees him as a threat. Never saw this coming. Never heard of such a thing until we started researching it. We love both cats, but refuse to live with one cat being mean to her brother. It’s like we brought home an unwelcome adopted cat... only it’s not. It’s her own brother that she grew up with. They are 4yrs old now. Very sad. ☹️

Tricia Cull April 30, 2020

Hi! We are experiencing the exact same problem. What was the outcome? Did you get Zoey to be friends with Andy again? Thank you!

Sofie March 10, 2023

I had the same problem with mine. I have two Male Rumble and Gnar who have been together almost their whole live apart from the first 3 months. Gnar is about 5 weeks older an a bit more dominant, but both are caring very much for each other with cuddling and cleaning each other. I had to take them to the vet. Initially only to get the teeth cleaned due to inflamed gum. That had to be done already early in their lives after only being 6 months old for the first time. The first time I had to take both and the second time 3 months later only Gnar. He seems to have poor genetics in this aspect. For these two times everything was normal and no aggressive behaviour to each other even when only Gnar had to go. After that I have brushed their teeth every day. This year, three years after the last time I had to take Gnar again for cleaning the teeth professionally. Since he has such problems with the teeth I took him to a vet who's specialised as dentist. It is a standard procedure for him to do an x-ray while the cat is under anesthesia anyway and found that a few teeth had FORL. So they did not only have to clean the teeth but also to pull some of the teeth. He was still extremely under the drugs, when I got home and he stank horribly even for me. I didn't hear of the non-recognition aggression before, and when I got home, I just let him off his box. He was still very confused with his surrounding and wanted to leave through the door, where we came in. It seemed like he himself did not recognise his home in that moment. The other one, Rumble, hurried to him to greet him and at first I did not recognise a difference, but then I noticed that while he was sniffing at Gnar he became very stiff and suddenly he started to howl. I am thankful now, that he did not lash out, but I was very worried. Are first I put on a cat harness trying to control the situation more, to hinder Rumble for a possible attack and so that Gnar could get some rest. But Rumble would not stop howling everytime he saw Gnar. The next thing I tried, was to put Rumble in a cat backpack which can be opened to a wider space. So maybe both could have a glance at each other, but not get in direct contact. After a few hours, when Gnar started to walk more again and wasn't sleeping anymore, I decided to separate them, but that made them both only stand directly at the door on each side. This is something what they always did, when I closed a door with one cat in another room. Besides that they don't like closed doors, they do not like it, not to have the opportunity to go to the other one whenever they like. So I first tried to feed them both each separated but directly at the closed door. When they tried to scratch at the door to signal it should be opened, my partner and I, each on either side of the door, put in skiing gloves to be able to intervene, if anything happens, and then We opened the door cautiously to let them sniff and see each other. They came very close and there was no fight. After a few minutes the howling of Rumble started again, so I seperated them again. My Partner and I tried to relax a bit to not signal stress from our side, but of course at least I was quite stressed. After a while, one of them was scratching the door again and we did the same thing. Cautiously opening the door. After that we all could relax a bit. Rumble did not start to howl again. He only headed a few times, but he kept his distance more or less for a while. When I was assured that it was unlikely, they'd fight, I could go to bed. Every day after that was one better than the other. After the first night, I heard a few hissing, but after about a week I guess they were totally back to normal. I am a bit anxious now, because Rumble needs to get through the same procedure because he has FORL which already can be said for two teeth without an x-ray, so he will get surgery and cleaning of the healthy teeth next week. This time I will try to do the trick with rubbing him with a blanket with their smell. If it does not work I'll try the tuna trick from this forum. I'm just hoping that this will not be as bad as last time, though in comparison to some stories here it surely wasn't that bad. But probably every one gets stressed out, when experiencing this and not knowing about this.

Nikki_P May 30, 2018

Hello! I posted this question on the article regarding gradually introducing new cats, but thought it would be appropriate to post on this thread, too, as it concerns feline non-recognition aggression. Thanks! -- We recently brought home our kitty, Mi-Go, from an extended stay at the vet. To our surprise, our other kitty, Binx, became extremely aggressive towards Mi-Go. We have since learned that this is called feline non-recognition regression and should have taken steps to reintroduce the cats slowly, much like is suggested in the article above. Unfortunately, it's been three weeks since Sir Mi-Go has been back home and we're just now finding this all out. To further complicate matters, Mi-Go is an extremely emotional cat and would come undone if we cloistered him away for a few weeks. No exaggeration, this cat is extremely sensitive and is prone to depression over the littlest thing (eg: we didn't "invite" him to sit with us on the couch, or we dared to shut our bedroom door). Binx, however, would probably do fine if we shut her in the master bedroom for a few days. We've actually done that very thing in the past few weeks when neither my partner nor I have been home to referee between the cats, and she seems very at ease in there by herself (of course, taking care to give her loves, treats, and attention when we return). My question is, do you think this will work to sequester the aggressive/threatened cat, Binx, or will it cause more harm to keep her from roaming freely through her house? Is the only way for this to successfully work to have Mi-Go, the returning cat, be the one that's tucked away? Also to note: We really love our cats and give them all a lot of affection and play time, and try to use positive reinforcement as much as possible. Also, we've tried Feliway, but it hasn't seemed to help in this situation. Any advice appreciated!

yelpot May 9, 2018

Firts I have to thank you for this article. I wish I had this Saturday . My Milo went to the groomer. When we arrived home my heart broke. Him and pepa we're so close. I feel so bad

BayouBlessings May 4, 2018

I wish I'd known about this! Yesterday I shaved my Maine Coon and now my other cat, who just adores him, hates him! I'm a groomer, so it's not like I took him somewhere else, but as soon as I finished his haircut, the other one screamed at him. They got into a terrible fight. I've separated them and will follow the guidelines of introducing a new cat. Thanks for the article!

Kez February 12, 2018

We have 17 month old brother sister siblings who we keep probably 97% of the time locked up inside. We have a large 4 bedroom house with a two and a half car garage all well equipped with several litter boxes, scratching posts, toys and plenty of free shelving for them to climb up on. They are only ever outside if we are home (they don't wander far) and we never leave them out at night either. We are very interactive with our cats, playing with them all the time, chat away to them - they quite often chat back (cute) Maisie especially likes to stay close but everything is on her terms when it comes to picking her up for cuddles where as Stuart loves cuddles and play fighting with my Husband. He is a bit of an explorer and will go for a wander to the paddocks behind us when allowed out. Stuart is a much larger cat than his sister Maisie and has on the odd occasion thought it would be a good idea to bail her up, much to her protest. We never hear Stuart letting out the blood curdling cat scream but Maisie will. What we are confused about is that Stuart, when confronted by any of the neighbour's cats, he either runs for his life or becomes quite submissive - much like Maisie when Stuart has a go at her. BUT. Maisie, as tiny as she is, has no problem having a go at any of the neighbourhood cats should she feel threatened, even coming to Stuart's aid if need be. Why do the roles get reversed and why does Stuart just randomly do this to Maisie? Any help or advise would be much appreciated as getting rid of either of them is not an option and if we can "nip" this in the bud now, would be great. Cheers from NZ

Threecozycats November 25, 2017

We think this could be happening with our two cats who are littermates. They got along just fine until about 1.5 years ago when the female started growling/hissing at the male every time he walked in The room and/or attacking him just for walking by. Want to say this started after a vet visit for the male being sick but cannot remember as it was so long ago. This behavior has progressively gotten worse despite feliway diffusers and calming collars. It’s gotten to the point where they cannot be in the same room together and she pretty much has isolated herself to our bedroom. Now the male is exhibiting anxiety and anxious behaviors and the fighting has just gotten worse. Is there any way to manage this now that it has been going on for so long? Feel like we have tried everything under the sun. Also both got a clean bill of health from the vet so we have ruled out any medical issues.

Ana April 5, 2022

Hi. Did they ever become friends again? 🥺

BangkokKittens November 24, 2017

Great article. I wish I had seen this before I tried to reintroduce a post surgery mother to her four kittens (see link below) Rescuing Feral Kitten In Bangkok I was so happy to reunite them that I just crudely dumped Mom back in the room with the kittens and it was a disaster. At first they were extremely hostile and stressed out. So, I pulled her out and tried several more times. I think the core issue was the she smelled and acted differently, but I think I made it worse by just dropping her into "their space" Following that I gradually reintroduced her several times, with a bit less hostility but not much satisfaction. I always made sure they were all fed first and if I fed them together made sure the food was spread out and abundant. Importantly, I later just opened the door to the room they were in and introduced her downstairs, so they could meet in a neutral territory. Over 10 days or so, they seemed to gradually get more comfortable with each other and finally seemed to actually like each other. Oddly, I didn't see them redevelop a maternal bond until yesterday when she broke them out of the house and led them on a madcap escapade. Now that I have trapped them and have them all bad in the house, they are finally a family again! Wow

furrypurry November 17, 2017

This has happened several times with my two Himalayans, even when they both go to the vet at the same time! They are littermates and have been together since birth. Jaspurr gets hissy and it can last for a week. Purrcy never hisses or acts aggressive, even if Jaspurr goes to the vet without him and comes home smelling weird. It stresses me out drastically because we usually have a very peaceful household. The one thing I have found that works is similar to rubbing the cats down with a familiar blanket, etc. I read about this and I was thrilled that it worked. BEFORE going to the vet, take a pair of clean socks and rub one cat down well with one sock, then rub the other cat down with the other sock. Be sure to rub around the face and the scent glands. Put both the socks in a zip lock bag together. Upon returning home, before you let them have contact, rub both cats down with BOTH socks, melding their scents. The time I did this we had ONE half-hearted hiss from Jaspurr and all was well after that.

dhruska211 November 16, 2017

Thank you for the article. I have an aggressive cat the only one I have 26-month-old kittens that iPhone a one-year-old seven is the aggressive 17 and 21. And Neighbor asked me if I would take the now seven-year-old and she was not socialized she had two cats of her own she kept this one confined. She is free to mingle with the other cats but I don’t keep any of them locked up I never did I have tried everything but you still mean. To make matters worse I didn’t know that she was the one eating all of the dry cat food..... I recently change diet completely she will have nothing to do with raw food. But she does need food so I gave her the dry. Furthermore she has attacked to pet sitters. Growls and hisses at my son and she has bit me. I have to go to the hospital for that one it was very deep I was folding laundry at the time. I have tried everything oh and she went after my neighbors one year-old grandson. At this point I think there’s something seriously wrong with this cat She can be very loving one on one but is soon as the other cats come around she is just miserable. Any suggestions because all my other cats are nice - But they don’t put up with her either

caracoveney November 15, 2017

This happened with two of my cats last year. I had to keep the younger in a cattery on its own for over a week whilst I 'cat-proofed' my garden, as he was getting ill by going into a neighbouring field, where there was a lot of ash. (The other two cats didn't wander into the field so were not at risk.) On his return, it was horrendous between my two. They had never been the best of friends but had been amiable enough, but the older cat treated the younger like a mortal enemy on his return! Snarling, spitting, swiping - it was awful for a couple of days I went onto a cat forum and a lady there suggested that I use a cloth on both cats, and then rub the 'mixed' scent onto each of them, then wipe it along things in the house and garden at 'cat height'. It was like magic. The effect was immediate. I have used this method ever since if one of the cats has had to stay at the vet for any reason.

debl58 November 9, 2017

We are going through this right now. Wish I had known this was a “thing” before taking the one cat to vet. I would have just taken both of them and avoided this nastiness. But at least I know now and hope the one that was left at home “wakes” up and realizes Loco is her baby brother she’s known for 5 yrs. great article, great advice.

How To Deal With Non-recognition Aggression In Cats